Note 24 — Chapter IV · PART I. THE AQUEDUCTS.

The source of the Appia was 780 paces off the road, between the 7th and 8th milestone. That of the Augustan 880 paces off, and by the 6th milestone. The former was measured to its termination, giving 11⅛ miles. The latter went only to the “Specus Vetus” (which is two miles less) and gave 6⅓ miles. Two miles is the distance from the Porta Maggiore to the Porta Trigemina and the Salaria. In all probability the Augustan branch was carried for the six miles into Rome along the bank of the Via Prænestina, here a deep foss-way between two high banks; and at a later period the Aqua Virgo was carried over it at a higher level, till within about half a mile of Rome, where it arrives at the outer bank of the great foss, and is carried at a sharp angle to the north to the Pincian. The Appia, being much deeper, was carried straight on at the bottom of the great foss into Rome, and entered at the extreme eastern corner, under the line afterwards taken by the Claudian arcade, to the two great reservoirs or gemelli before mentioned; the main line running here parallel to it, a little to the south, till it reached the Piscina of S. Helena, the two lines converging at the gemelli.